PROJECT SUMMARY Over the past few years there has been an accelerating expansion of oral anticancer drugs. These drugs are expensive and cost up to $10,000/month. To counteract increasing medication costs, pharmacy benefit plans have increased copayment rates, deductibles and increased preauthorization. We propose to define barriers to initiation and non-adherence to anticancer medications that are considerably more expensive and the acquisition is more complex that other cancer and non-cancer therapies. We propose conduct a prospective cohort study among a diverse population of cancer patients prescribed non-hormonal oral antineoplastic agents, to define barriers to acquisition, initiation and first prescription renewal and we will conduct semi-structured interviews on a subset of 30 participants. We hypothesize that the increasing costs and subsequent complexities in acquisition associated with oral medications results in delays and barriers to access due to the administrative burden on the practice. Our specific aims are (1) to determine the rate and factors associated with non-initiation of oral antineoplastic agents in a socioeconomically, racially and ethnically diverse cohort of 750 patients prescribed oral cancer therapy. (2) To define the time (days) to initiation of antineoplastic treatment and factors contributing to longer initiation time. (3) To examine factors related to early discontinuation of oral antineoplastic agents (<90 days) among those who initiate. (4) To explore patient perceptions on the medication acquisition process. The goal of this proposal is to define and characterize the extent of use of these new expensive oral therapies, as well as to determine human costs and insurance related factors associated with delays in initiation and early discontinuation. We will determine the extent to which financial factors contribute to disparities in use. Results will inform policies and assist with the design of interventions to improve the quality and safety of oral medication use in oncology care.